The invention relates to a device for switching and elastically locking the end positions of movable switch parts, in particular switch tongues of grooved rail switches, including an axially displaceable rod and a tube surrounding the rod, in which a spring encompassing the rod is braced against stops and locking members capable of being displaced radially outwards are arranged, wherein the rod has axially spaced-apart control stops for a radially inward position of the locking members and the tube has stops for the outward position of the locking members.
In addition to using a so-called switch lock including a clamp-like catch unit to lock movable switch parts, EP 603 156 A1 has already suggested a configuration in which extra-axial loads on the lock are avoided, enabling the realization of a completely closed mode of construction. In that known locking device, which may also be used as a switching aid with the appropriate arrangement of pressure springs, a rod is arranged in an axially displaceable tube, which, in turn, is itself arranged in a stationary tube. Locking members were displaceably guided within the axially displaceable tube in the radial direction, and recesses were each provided in the stationary tube and in the rod to cooperate with the locking members during displacement and in the end position. When using such an arrangement as a switching aid in support of the displacement movement, two pressure springs were used, which involved high overall expenditures in terms of construction. Embodiments of a switching aid are also known from AT 379 624, which uses a spring rocker in which an angle lever is mounted in the crossing point of the arms, wherein a force accumulator is supported against the arms of the two angle levers by means of a pressure spring. Two spring rockers were connected with the two tongue rails via coupling rods.
From Austrian application A 2137/97 a switching aid used to elastically lock movable switch parts is known, in which locking members are mounted in an axially spaced-apart relationship in cages arranged between a tube and a rod, a pressure spring acting in the axial direction being arranged between those cages. The rod is connected with the tongue rails via coupling rods, wherein control grooves are provided about the periphery of the rod to move the locking members into their different positions such that the pressure spring will be tensioned during the switching procedure and exert an application force on the tongue in the position of abutment of the tongue on the grooved rails. The ball cages are axially movable to a limited extent such that they may be used with different tongue impacts or different transverse movements of the tongue. The pressure spring in those known devices exerts different forces on the tongue, depending on the tension length.
In EP-A1 603 156 different locking arrangements and switching aids are described with an actuating means being arranged between two substantially identically constructed switching aids. In the main, such configurations have relatively large structural lengths, thus rendering their use with small rail gages and, in particular, grooved rails not readily feasible.
From FR-A-2 523 537 a switching aid comprising an integrated hydraulic actuating means has been known, wherein spring rockers are designed in the form of two pressure springs which are supported on the housing of the ground box and enter into effect as predetermined dead center positions have been exceeded. Finally, EP-A1 0 779 197 discloses a device for securing the end positions of hydraulic actuating drives.
All known devices have in common that their displacement strokes cannot be readily changed and adapted to the respective requirements.
The invention aims to provide the conditions for a compact short-structured actuating and switching aid which is suitable, in particular, for use in grooved rails because of its short structural length and which ensures that the resilient force of application on the tongue will become effective irrespective of a respectively adjustable active displacement path in order to enable the creation of constant application forces on the tongue irrespective of the displacement stroke. Due to the compact mode of construction, also the possible occurrence of transverse forces is to be reduced so as to enable a substantial reduction of wear.
To solve this object, the configuration according to the invention essentially consists in that at least one of the control stops is fixable to the rod in a manner displaceable in the axial direction of the rod. Due to the fact that at least one of the control stops is fixable to the rod in a manner displaceable in the axial direction of the rod, it is feasible in a simple manner to adjust the stroke and hence the respectively required displacement path, the displaceability and fixability of the control stops, at the same time, ensuring that the full and constant spring force becomes effective at the end of the stroke.
In this context, the configuration according to the invention in a particularly simple manner may be devised such that the rod is dividedly designed, wherein the axial position of a rod part carrying a control stop is variable relative to the other rod part. The change of the axial length of the rod part with the simultaneous axial shift of the control stop, in principle, may be realized in different ways. If the axial length of one rod part is changed relative to the other rod part, this may be effected, for instance, in that one rod part is designed to have an external thread and the second rod part is designed to have an internal thread, the rod part having the external thread being screwed into, or out of, the rod part having the internal thread. In a particularly simple manner, the configuration may be devised such that the adjustable control stop is designed as an end face of a sleeve which is capable of being screwed on the rod and connected on its free end to the movable rail part via the coupling rod.
Such a sleeve carrying the adjustable control stop may be screwed on the rod in a simple manner and is easily adjustable even subsequently. Above all, such a device also can be secured against unintentional displacement, and arrested or blocked in the respectively selected position of the sleeve, in a particularly simple manner. To this end, the configuration preferably is devised such that the sleeve comprises an internal thread into which a locking piece carrying an external thread may be screwed in abutment on the rod in the manner of a counternut.
In order to comply with the requirements of a particularly compact mode of construction and hence ensure the preferred aptness for grooved rail switches, the configuration advantageously is devised such that the actuating means is comprised of a displaceable cylinder piston unit integrated in the tube coaxially with the axis or rod, the maximum displacement path of which cylinder piston unit is larger than the admissible adjustment range of the control stop or sleeve, respectively. Such an integration of a hydraulic actuating means in the switching and locking device results in particularly short dimensions and, at the same time, a reduced risk of eccentric off-center forces that might involve an increased wear. Particularly compact dimensions may be obtained if the piston of the cylinder piston unit is rigidly connected with the rod, the piston rod being identical with the rod carrying the control stops.
A configuration secured against the penetration of dust may be obtained in that the tube is closed by end faces on both sides, wherein, in a manner known per se, the locking members preferably are designed as balls and radially guided in axially displaceable cages with the spring being arranged between the mutually facing end faces of the cages.
In order to ensure the safe operation of the switching device even from the end positions, the configuration advantageously is devised such that the cages are located in end positions of the displacement path at a distance from the end faces of the tube.